Sensor devices making use of forward scattering principle are widely employed for atmospheric and meteorological studies, for example for measurement of atmospheric visibility and/or for precipitation measurements. Herein, we refer to such a sensor device as a forward scatter sensor.
The measurements carried out using a forward scatter sensor are based on analysis of the light scattered from particles in the atmosphere: a transmitter sends a conical light beam towards a receiver such that it is offset from a direct path between the transmitter and the receiver, whereas the receiver captures light scattered from the particles in the atmosphere. The receiver provides a signal that is descriptive of the captured light to a processing unit that may then compute meteorological parameters of interest related to visibility and precipitation.
Even though providing a well-working framework for analysis of certain parameters related to visibility and precipitation, known forward scatter sensors provide, however, limited capability for detailed analysis of precipitation while they also provide limited accuracy and reliability especially at low intensity precipitation events. Moreover, a forward scatter sensor for atmospheric and meteorological studies is typically installed outdoors for continuous operation and it may remain operational for several years. The environmental conditions may cause gradual soiling and wear of optical (and other) components of the forward scatter sensor, which in turn degrades accuracy and reliability of the measurement results obtained from the forward scatter sensor. Another factor that may affect the measurement performance of the forward scatter sensor is that due to continuous operation in field conditions it is susceptible to external impacts that may not be sufficient to cause actual damage but that may still have a detrimental effect to the alignment between the transmitter and the receiver, thereby possibly leading to compromised measurement performance.